iOS Localization

This post will show you how to localize your iOS apps, so they can be translated to several languages. The post will describe how to translate plain text and how to create localized versions of your storyboards.

Since storyboard localization comes with a few quirks, the post will discuss how to automate synchronizing changes that are made in storyboards.

Translating strings programmatically

Getting localization to work in iOS is really straightforward. You just have to do the following:

  • Add a new Localizable.Strings file to your project.

  • In this file, add key-value-based translations, like this (note that each line has to end with a semi-colon):

"key_1" = "Translation 1";
"another key" = "Another translation";
  • To create a localized version of Localizable.Strings, select the file in the Project Navigator and add localizations in the File Inspector to the right.

  • When you have more than one version of this file, an arrow will appear next to the file in the Project Navigator.

  • Click the arrow to show all localized versions. Select any version in the list to modify that version.

Note that once the localized versions are in place, any additional keys that you add must be added to all localized versions. The same goes for removing keys.

Once you have a couple of translations in place, use NSLocalizedString(key, ...) to translate any keys in the file:

NSLocalizedString("key_1", nil)

This will return “Translation 1”, if English is currently used. If you change to Swedish, the app would select the Swedish localization, if such a version exists. Any missing keys will default to the translation in the base version of the file.

That’s really all there is to it. Before moving on, I just want to give you some advice.

First, do not use this approach to translate your storyboards. This requires a separate IBOutlet for each component that should be translated. If you just have a few controls to translate, fine, but please read on to find out how to do this in a better way.

Second, I want to advice against using translation key strings directly in code. Doing so makes your app vulnerable, since a translation will fail if a string is mistyped. These kinds of “bugs” are hard to find, since the Objective-C compiler will not detect incorrect strings.

Instead, use a separate file that contains a definition for each key, as well as a translation macro with only one parameter (for convenience). In my latest app, I call it AppStrings.h, and it looks something like this (drastically reduced):

#define STR_CANCEL @"cancel"
#define STR_DELETE @"delete"
#define STR_OK @"ok"

#define Translate(key) \
[[NSBundle mainBundle] localizedStringForKey:(key) value:@"" table:nil]

As you see, this requires a bit of extra work since you have to add a definition for each translation key. However, it provides you with a clean interface, where keys strings are only used in this file. If a translation fails, this is the only place where it can be misspelled. All other classes will use the definitions.

You can then use the Translate macro (or the native NSLocalizedString, even if it requires two parameters; the Translate macro is just a convenience) together with any definition to translate your strings, for instance:


Translating storyboards

Translating text programmatically turned out to be really simple. Now, let’s see if translating storyboards is as simple.

Basically, you have (at least) two options:

  • Add an IBOutlet for each outlet that should be localizable, then translate it programmatically using the approach above

  • Enable localization for your Storyboard and add a separate storyboard variant for each language you have to support.

As I wrote above, do not use the first option if you have a lot of components to translate in your storyboard. That will result in a lot of outlets.

Instead, I suggest that you enable localization by doing the following:

  • Select your Storyboard in the Project Navigator

  • To create a localized version of the file, select it in the Project Navigator and add localizations in the File Inspector to the right.

  • When you have more than one version of this file, an arrow will appear next to the file in the Project Navigator.

  • Click the black arrow to show all localized versions of the storyboard.

You can now edit any version of the storyboard drectly. Translate texts, replace icons etc. That is it - simple, eh? Well, not really. Once you have your versions set up, you will bump into this:

  • You have an original storyboard

  • You create a localized version of the storyboard

  • You make changes to the original storyboard, such as adding or removing something

  • BOOOOM! The changes will not be made to the localized version of the storyboard

Since XCode does not keep the storyboards in sync, localizing early will resul in tremendous amount of extra work. Each change has to be done in each localized version…and that is just baaaaad.

Luckily, I found this great Python script that keeps your storyboards in sync:

Watch the video to find out how to make the script keep all storyboards in sync, each time the project is built. If you don’t have five minutes to spare, you can download the script here and add the following as a build step:

python [path to the python script] --mainIdiom=[the main idiom] --mainStoryboard=[path to the main storyboard] [list of idioms to translate]


Localization is easy. Localization is alright. Yes you should. Just do it right.